Integrated circuits may be formed on a semiconductor substrate such as a silicon wafer or other semiconducting material. In general, various materials which are semiconducting, conducting, and/or insulating are used to form the integrated circuits. By way of examples, the various materials can be doped, ion implanted, deposited, etched, grown, etc. using various processes. A continuing goal in semiconductor processing is to continue to reduce the size of individual electronic components thereby enabling smaller and denser integrated circuitry.
Memory is one type of integrated circuitry, and is used in computer and other electronic systems for storing or managing data. One type of circuitry component is the transistor. Memory may be fabricated in one or more arrays of individual memory cells which may include a transistor. Memory cells may be written to or read from using data/sense lines, for example a digit or bit line, and access lines (which may also be referred to as word lines). The data/sense lines may electrically interconnect memory cells along columns of an array, and the access lines may electrically interconnect memory cells along rows of an array. Each memory cell may be uniquely addressed through the combination of a data/sense line and an access line.
Memory cells may be volatile, semi-volatile, or non-volatile. Non-volatile memory cells can store data for extended periods of time, in many instances including when the computer is turned off. Volatile memory dissipates and therefore requires being refreshed/rewritten, in many instances multiple times per second. Regardless, memory cells are configured to retain or store information/data in at least two different selectable states. In a binary system, the states are considered as either a “0” or a “1”. In other systems, at least some individual memory cells may be configured to store more than two levels or states of information.
Integrated circuitry fabrication continues to strive to produce smaller and denser integrated circuits. Accordingly, there has been substantial interest in non-volatile memory cells that can be used in structures having programmable material between a pair of electrodes. Examples of such memory cells are resistive RAM (RRAM) cells, phase change RAM (PCRAM) cells, programmable metallization cells (PMCs) which may be alternatively referred to as a conductive bridging RAM (CBRAM) cells, nanobridge memory cells, or electrolyte memory cells. The memory cell types are not mutually exclusive. For example, RRAM may be considered to encompass PCRAM and PMCs.
One example programmable material of an RRAM cell comprises a multivalent metal oxide portion and an oxygen-containing dielectric portion. Such materials may be programmed by moving oxygen species (for instance, oxygen ions) within and between the different portions.